The present invention relates to apparatus enabling a feed or an exhaust pneumatic path for a pilot circuit common to an island of electropneumatic control valves to be selected from at least one of two available paths.
In the field of electropneumatic automation, installations have control valves for feeding actuators with air under pressure and for enabling said air under pressure coming from said actuators to be exhausted. The installation responds to commands which sequence successive switching operations of the valves in order to carry out the functions of the installation. The switching is obtained by moving a moving member internal to the control valve from one position to another. The energy required for moving the member can be purely electromagnetic or it can be pneumatic and taken from a pneumatic pilot circuit that includes a solenoid valve. The pressure that exists in the pilot circuit is generally applied sequentially to one or other of the ends of the moving member inside the control valve.
For many years, control valves of this type have been associated with respective bases each containing at least one pressure channel and at least two service orifices for connection to the actuator controlled by the control valve. Such bases enable a plurality of control valves to be grouped together as a single block (island) in which the valves are served by a common pressure channel passing through all of the bases that are grouped together.
In a manner similar to feeding an island of control valves in common, bases have more recently received at least one segment of an exhaust channel so as to provide one or two common exhaust manifolds for actuators, with said segment thus co-operating with the bases of the island to form one or two exhaust manifolds.
In that kind of architecture, internal branch channels have also been provided firstly to convey the pressure that exists in the pressure manifold of the bases to a secondary channel for feeding solenoid valves that pilot the control valves, and secondly for connecting the exhaust manifold from the control valves to a secondary channel for combining the exhausts from the solenoid valves.
However, in some cases, applying working pressure to the pilot valves is not appropriate; this pressure can be too low, for example lower than atmospheric pressure in a vacuum installation. In addition, it can be useful to be able to cut off pressure in the pilot circuit without simultaneously cutting off pressure from the installation: e.g. under circumstances where the user needs to take the function of piloting the control valves out of operation without having to act on the electrical circuits of the pilot valves. Furthermore, when it comes to collecting exhausts, it can be advantageous to separate the collection of pilot exhausts from the main manifold for collecting exhausts from the control valves, in order to avoid exhaust back pressures being generated by high flow rate actuators, which back pressures can then act on the piloting of the control valves.
As an alternative to such internal channels for feeding pressure to and for collecting exhausts from the pilot circuit, and also to rationalize the manufacture of pneumatic components, provision has been made to fit such internal channels with respective selectors whose positions define the connections of the pilot circuit as being either to the common pressure or exhaust channel, or else to a separate external duct.
In a set of control valves constructed as an island, the common pressure channel and the common exhaust channel(s) are connected to the outside of the island via at least one end module, optionally together with one or more intermediate modules, particularly if a plurality of pressure thresholds are used, thus providing an interface between the island and external pressure-feed and/or exhaust-collection ducts.
The present invention relates to the interface module fitted with at least one selector whose function is to ensure that pilot feed and/or exhaust is selectively connected either to the common pressure or exhaust channels of the bases, or else to a corresponding external duct, depending on the position of the selector. In addition, the module includes the means for connecting an external duct to the pilot channel pressure feed and/or exhaust of an island.
More precisely, the present invention provides an interface module for an island of electropneumatic control valves on bases, the module comprising a body having at least one face for connection to a base of the island and, away from said base, means for coupling to at least one first external duct. The body also having at least one internal main channel, at least one secondary channel, and a branch internal channel for connecting the main channel to the secondary channel, which branch channel is provided with a two-position selector which, depending on its position, provides continuity for the connection or interrupts it.
According to the invention, the selector has connection means for connecting the secondary channel to a second external duct, which means are accessible from outside the module when the selector is in its interruption position and are masked when the selector is in its continuity position.
These connection means can be of any conventional type, such as a quick coupling endpiece or an externally or internally threaded orifice, such that they constitute a display member for any person taking action, which member, when visible, indicates that the solenoid pilot circuit of the island in communication with the secondary channel of the body needs to be connected to an external duct, regardless of whether the external duct is a feed duct or an exhaust collector duct (or more simply, for the exhaust, to an exhaust silencer leading to the surrounding air and connectable via the same means), whereas if said coupling member is not visible, then pressure feed or exhaust collection for the solenoid valve pilot circuit of the island is provided internally.
In an advantageous embodiment, the selector overlies the above-mentioned body, co-operating therewith via a face that is perpendicular to its face for connection to the bases, and it is covered by a cap for masking the connection means for connecting the selector to said second external duct when the selector is in its continuity position.
When it is used for pilot pressure, the main module channel concerned by the selector is a pressure channel, and the secondary channel is a channel for feeding the pilot circuit.
The selection function can also apply to exhaust from the pilot circuit depending on whether or not it is desired for the exhaust to join the exhaust manifold provided in the bases, which depends on the exhaust back pressures that might exist in the exhaust manifold. Under such circumstances, the above-mentioned module main channel is an exhaust channel and the secondary channel concerned by the selector is a common channel for collecting pilot exhaust or an exhaust silencer leading to the surrounding air.
An island of control valves on bases can lie between two interface modules located at respective ends of the island. One of the modules can be concerned only with connecting the island to the working pressure source and optionally to an auxiliary pressure source for pilot purposes, while the other module can be concerned only with providing common collection of exhaust from the control valves and optionally with collecting pilot exhaust. However, in preferred manner, an island has only one end module which serves both to connect the island to the working pressure source and optionally (depending on the position of the selector) to the auxiliary source for feeding the pilot circuit, and also for collecting exhaust from the actuators and optionally exhaust from the pilot valves. Under such circumstances, the module includes two superposed selectors, one for the pressure circuit and the other for the exhaust circuit.
Mention is also made of the optional existence of intermediate modules located between two base blocks which, for example, serve to isolate one block from the other so that the blocks can be fed with different pressures, with the intermediate blocks nevertheless being transparent so far as exhaust is concerned. Such intermediate blocks can be fitted with selectors of the invention.
Finally, according to a secondary characteristic of the invention, in order to satisfy certain ergonomic and appearance criteria, the connection means carried by the selector, when accessible, are situated on the same face of the module as carries the means for connection to the first external ducts, i.e. the ducts for feeding working pressure and the ducts for collecting exhaust.